Disk drives are capable of storing large amounts of digital data in a relatively small area. Disk drives store information on one or more recording media, which conventionally take the form of circular storage disks having a plurality of concentric circular recording tracks. This information is written to and read from the disks using read/write heads mounted on actuator arms that are moved from track to track across the surfaces of the disks by an actuator mechanism.
Generally, the disks are mounted on a spindle that is turned by a spindle motor to pass the surfaces of the disks under the read/write heads. The spindle motor generally includes a shaft mounted on a base plate and a hub, to which the spindle is attached, having a sleeve into which the shaft is inserted. Permanent magnets attached to the hub interact with stator windings on the base plate to rotate the hub relative to the shaft. In order to facilitate rotation, one or more bearings are usually disposed between the hub and the shaft.
The bearing assembly that enables the rotation of the storage disk is of critical importance. One bearing design is a fluid dynamic bearing. In a fluid dynamic bearing, a lubricating fluid, such as air or liquid, provides a bearing surface between a fixed member of the housing (e.g., a shaft) and a rotating member of the disk hub. In addition to air, typical lubricants include gas, oil, or other fluids. Fluid dynamic bearings spread the bearing surface over a large surface area, as opposed to a ball bearing assembly, which comprises a series of point interfaces. The large bearing surface distribution advantageously reduces wobble or run-out between the rotating and fixed members. Further, the use of fluid in the interface area imparts damping effects to the bearing, which helps to reduce non-repeatable run-out. Thus, fluid dynamic bearings are an advantageous bearing system.
Many current fluid dynamic bearing motors use capillary seals because they are capable of holding a large volume of reserve oil for increased evaporation life. However, this design is susceptible to oil leaking when subjected to shock acceleration. This loss of lubricating fluid reduces motor life and contributes to drive contamination issues, and ultimately motor failure.
Therefore, a need exists for a capillary seal design that reduces oil leakage or spillage with shock.